A plant cultivation device (1) comprising at least one light source (4) from which light is irradiated downward to a plant (P) that is planted in a medium (2), and a transparent protective plate (5) which is positioned between the medium (2) and the light source (4) and allows the transmittance of the light that is emitted from the light source (4) toward the plant (P), wherein the transparent protective plate (5) is held at an arbitrarily defined height from the medium (2) and regulates the elongation of the plant (P) toward the side of the light source (4).
